Brain

A chimpanzee brain

The brain is a part of the body that allows us to make sense of the world around us and to change our behavior to respond to it. Our brain is the control center of the whole body. It receives messages from all parts of our body and sends out necessary commands to control the body's actions. The brain is made up of a special type of cells. They are connected with each other and with the nerves in our body. The delicate brain is protected on the outside by strong skull bones.

Jobs

The brain does the thinking, learning, and feeling for the body. It is the source of consciousness, but it also controls basic body actions, like breathing, that happen without a person realizing it. All the information about the world gathered by our five senses is sent through nerves into the brain, allowing us to see, hear, smell, taste and feel things. The brain processes this information so that we can experience it as pictures, sounds, and so on. The brain also uses nerves to tell the body what to do, for example by telling muscles to move or our heart to beat faster.

Evolution

Most animals have brains, in some way or another. Some animals, however, like jellyfish, do not have brains. Over time, animals' brains have become more complicated because of evolution.

Humans might have the most complicated brain. People used to think that only humans had a sense of humor, but apparently the octopus also has a sense of humor. Over time animals' brains also gained the ability to have emotions, but scientists are still not sure what defines emotions and which animals have them.

Parts

In human beings, the brain is made of three main parts: the cerebrum, the cerebellum and the brainstem. The cerebrum is where intelligence and thought is. The cerebrum lets us learn, reason, remember, create (make), and think. It also controls the senses and the muscles. The cerebellum connects all the muscles so they can work together. The brain stem is something that connects the brain with the spinal cord. It has lots of different parts that control different jobs in the body: for instance, the brain stem controls breathing, heartbeat, sneezing, eye blinking, and swallowing. Body temperature and hunger are also controlled by parts of the brain stem.

A human brain accounts for about 2% of the body's weight, but it uses about 20% of its energy. It has about 50-100 billion nerve cells (also called neurons), along with roughly the same number of support cells, called glia. The job of neurons is to receive and send information to and from the rest of the body, while glia provide nutrients and guide blood flow to the neurons, allowing them to do their job. Each nerve cell has contact with as many as 10,000 other nerve cells through connections called synapses.

Size

The volume of the human brain (relative to the size of the whole body) is very large, compared to that of most other animals. The human brain also has a very large surface (called cortex) for its size, which is possible because it is very wrinkled. If the human cortex were flattened, it would be close to a square meter in area. Some other animals also have very wrinkled brains, such as dolphins and elephants. Some people believe that what makes humans so smart is the large volume or surface area of their brains, but there is no evidence for a relationship among animals between size of the brain and intelligence; e.g. the brain of a blue whale is much heavier than a human brain, but it is not seen as being more intelligent than a human's brain. As an additional note, Einstein's brain weighed only 1,230 grams, which is less than the average adult male brain (about 1,400 grams).

Other pages

• Spinal cord
• Vertebrate brain

Other websites

Wikimedia Commons has media related to:

Brain

• Sylvius: 400+ structure neuroanatomical visual glossary; used by over half of U.S. medical schools
• High-Resolution Cytoarchitectural Primate Brain Atlases
• Human Brains: A Learning Tool.